1. Technical Field
The invention relates to a method of registering a running time on an information carrier, the information carrier comprising main data and subcode data, the running time being indicated in a subcode channel by a subcode time expressed in accordance with a predetermined format.
The invention also relates to a method of registering a running time of an information carrier, the running time being described by a subcode time in a subcode channel, the subcode time being expressed in minutes, seconds and frames, a number of bits for expressing the number of minutes of the subcode time being available in the subcode channel.
The invention further relates to an information carrier comprising main data, subcode data and tracks in which information is stored, the information carrier further comprising information about a running time of the information carrier, the running time being indicated in a subcode channel by a subcode time expressed in accordance with a predetermined format.
The invention further relates to an information carrier for recording and storing main data and subcode data in tracks, the information carrier further comprising a pre-groove in which information about a running time indicated by a subcode time and a pre-groove time is stored, both the subcode time and the pre-groove time being expressed in accordance with a predetermined format.
The invention further relates to an apparatus for reading an information carrier, comprising a system for detecting and reading information stored on the information carrier, the system comprising detection means and read-out means for receiving detector signals, the read-out means being arranged to retrieve a subcode time.
The invention further relates to an apparatus for recording an information carrier, comprising write means for inducing a detectable change on a layer of the information carrier, the write means being arranged to write a subcode time on the information carrier, which subcode time is incremented in accordance with an actual tempo, the actual tempo representing a tempo in accordance with the actual running time.
The method according to the invention may be used in several well-known information carriers, e.g. Compact-Disc (CD), Video-CD, CD-Recordable (CD-R) or CD-Rewritable (CD-RW).
2. Related Art
A method mentioned in the foregoing is known from the standard format description of the Compact Disc Digital Audio, well known to the person skilled in the art (see International Standard IEC 908).
In this standard format description, a high-density optical disc is described in detail. The digital information present in digital form on this disc is read out by means of an optical system. Using the EFM-modulation code and the CIRC error-correction system for storing information on the disc, an information carrier with reasonably good error-detection and error-correction possibilities is created. In order to create these possibilities, redundancies are used in the EFM-modulation code.
After demodulation, some bits are present for control and display purposes. With these bits, the standard format description of the Compact Disc defines eight additional channels of information or subcodes that are added to the music information; these subcode channels are called P, Q, R, S, T, U, V, W. One of the features of the Q-channel states the running time of the information carrier. The invention relates to this feature.
It should be noted that the Compact Disc Digital Audio is only to be taken as an example in the field of application of this invention. Other different CD formats can be used to apply this invention, e.g. Video-CD, CD-R or CD-RW. For example, in the CD-R or CD-RW, the running time as described below in detail is recorded in the so-called pre-groove in the ATIP (absolute time in pre-groove). For an overview of some relevant CD standards, see Compact disc standards: an introductory overview, Jan Korst, Verus Pronk, Multimedia Systems (1994) 2:157-171.
According to the standard format description of the Compact Disc Digital Audio, the running time on the disc is expressed in 6 digits in BCD-code. The fields AMIN, ASEC and AFRAME are each expressed in 2 digits. This has as the effect that the maximum value of the AMIN field is 99 minutes, resulting in a maximum running time of almost 100 minutes (in fact, 99 minutes, 59 seconds, 74/75 seconds, as will be further explained).
A person skilled in the art therefore learns from the standard format description that the running time of a Compact Disc is limited to 100 minutes, which is due to the fact that 2 digits are available for expressing the AMIN field.
In certain circumstances, it may be desirable to increase the possible maximum running time of the Compact Disc. The invention therefore has for its object to provide a running time registration with an increased possible maximum running time on an information carrier.
The method according to the invention is characterized in that a pseudo-running time is described by incrementing the subcode time in accordance with a pseudo-tempo, which is different from an actual tempo, the actual tempo representing a tempo in accordance with the actual running time.
The invention is based on the recognition that, by incrementing the subcode time at a pseudo-tempo which is different from an actual tempo, the actual tempo representing the actual running time of a Compact Disc as indicated by the subcode time is not limited to 100 minutes anymore. By using this pseudo-tempo, more flexibility in the maximum achievable running time is introduced.
Technical improvements have made it possible to increase the running time of a Compact Disc, starting from an initial value of approximately 72 minutes. Due to these improvements, the maximum possible subcode time of 99:59:74 may be a limiting factor to the running time of a Compact Disc. By introducing the proposed subcode time according to the invention, the subcode time ceases to be a limiting factor.
Another method according to the invention is characterized in that the pseudo-tempo is smaller than the actual tempo.
By using a pseudo-tempo that is smaller than the actual tempo, the subcode time exceeds the known limit of 100 minutes.
Another method according to the invention is characterized in that a first pseudo-tempo is equal to the actual tempo up to a predetermined subcode time, and that, starting from said predetermined subcode time, a second pseudo-tempo is smaller than the actual tempo.
Depending on the actual running time of an information carrier, it may be favorable to use a tempo which is equal to the actual tempo up to a predetermined subcode time and, after that subcode time, a tempo smaller than the actual tempo. In this way, the user of this information carrier has the correct information about the running time up to that subcode time. After that subcode time, the displayed running time information is not correct anymore.
If an information carrier has a total running time of 120 minutes, up to 80 minutes of the actual tempo is used, resulting in a correctly displayed running time information. After 80 minutes, a pseudo-time equal to half the actual tempo is used, resulting in a total possible subcode time of 120 minutes. It is clear therefrom that the choice of the pseudo tempo and the predetermined subcode time is dependent on the total running time of the information carrier used.
Another method according to the invention is characterized in that a first pseudo tempo is equal to the actual tempo up to a predetermined subcode time and that, starting from that predetermined subcode time, a second pseudo tempo is zero.
Instead of using a tempo smaller than the actual tempo, a zero tempo may also be used. This results in the subcode time being kept constant. Therefore, there is no limit to the running time of the information carrier anymore. The running time displayed is not in accordance with the actual running time of the information carrier, starting from the predetermined subcode time.
Another method according to the invention is characterized in that a control code is used, this control code indicating the use of a subcode time in accordance with a pseudo-tempo which is different from the actual tempo.
By using a control code, e.g. a pointer, in the subcode channel, the use of a subcode time which is different from the xe2x80x98regularxe2x80x99 subcode time can be indicated. This control code can be stored in the subcode time at the place where the xe2x80x98regularxe2x80x99 subcode time is abandoned. With this information, the apparatus reading the information carrier can, for example, display an additional sign indicating that the running time displayed does not correspond to the actual running time.
Another method according to the invention is characterized in that the pseudo-tempo is smaller than the actual tempo by expressing the subcode time in values exceeding the maximum possible values in accordance with the predetermined format.
By expressing the subcode time in values exceeding the maximum possible values in accordance with the predetermined format, the maximum possible running time is increased. The maximum possible values in accordance with this predetermined format are 59 for AMIN and 74 for AFRAME. Optimally use of the predetermined format with the subcode will result in a maximum value of 99 for AMIN and AFRAME. As the subcode addresses are in accordance with the predetermined format, there will be no problems when reading an information carrier with these subcode addresses.
Another method according to the invention is characterized in that the number of bits is increased by using bits, which are present in fields of the subcode channel, the field having a predefined purpose different from expressing the minutes of the subcode time.
In order to increase the running time, different subcode timing bits may also be used. Bits which are present in fields of the subcode channel can be used for expressing the minutes of the subcode time. These fields have a predefined purpose which differs from that for expressing the minutes of the subcode time.
The information carrier according to the invention is characterized in that a pseudo-running time is described by incrementing the subcode time in accordance with a pseudo-tempo, which is different from an actual tempo, the actual tempo representing a tempo in accordance with the actual running time.
Another information carrier according to the invention is characterized in that a pseudo-running time is described in the pre-groove by incrementing the subcode time in accordance with a pseudo-tempo, which is different from an actual tempo, the actual tempo representing a tempo in accordance with the actual running time.
The apparatus according to the invention is characterized in that the read-out means are further arranged to detect a control code indicating the presence of a subcode time which is incremented in accordance with a pseudo-tempo, which is different from an actual tempo, the actual tempo representing a tempo in accordance with the actual running time.
Another apparatus according to the invention is characterized in that the write means are further arranged to write a subcode time on the information carrier, which subcode time is incremented in accordance with a pseudo-tempo which is different from an actual tempo.